A typical prior art solenoid valve apparatus consists essentially of two valves, and one solenoid for the actuation of the two valves. The solenoid has two armatures, one coil, and one core. The first valve is a 3/2-way valve, via which the end-user can be connected at will to a pressure fluid source or to a pressure fluid sink. The second valve, which is a switch-controlled throttle, precedes the first valve.
In a first switch position of the first and second valves, the pressure fluid goes from the pressure fluid source through a large cross-section passage of the second valve, and through the first valve to the end-user, without being throttled.
In a second switch position of the first and second valves, the end-user is shut off from the pressure fluid source by means of the first valve, and is connected to the pressure fluid sink. The pressure fluid then travels in a throttled state, via a small cross-section passage of the second valve, from the pressure fluid source to the pressure fluid inlet of the first valve. If the two valves are again switched over, with the second valve returning (with delay) to its first switch position, the pressure fluid flows in a throttled state from the pressure fluid source to the end-user. As soon as the second valve has returned to its first switch position, the pressure fluid flows from the pressure fluid source to the end-user, without being throttled.
This prior art solenoid valve apparatus is simple and compact in structure. However, without any additional measures being taken, it can only be used to control the pressure for one end-user.
Therefore, an object of the present invention is to create a simple solenoid valve apparatus of the type described above, with which it is possible to connect two end-users to a pressure fluid source, as well as to close off the two end-users from the pressure fluid source.
The present invention offers the advantage of providing a solenoid valve apparatus which carries out more functions than the prior art solenoid valve apparatus, but which also has a simple and compact structure.
It is a special advantage of the inventive solenoid valve apparatus that not only can two end-users be selectively connected to, or closed off from, a pressure fluid source or a pressure fluid sink, but in addition, the two end-users can also be closed off from each other.
It is also possible to omit the installation of a core in the inventive solenoid valve apparatus, without significantly reducing the effectiveness of the inventive solenoid valve apparatus. The core could be replaced by a separating wall that is as thin as possible, and is made in one piece with an armature-guiding tube, so that it subdivides the armature-guiding tube into two segments.